Certain types of food consistencies need a little prep before testing.
To help prevent errors, you can crush or cook hard foods (nuts, frozen peas), rip or chop dense foods (well-cooked meat) and emulsify or dilute powdery foods (dry spices), creamy (chowder), thick (think sauces) and high fat foods (yogurt, frosting).
Puffed foods, specifically puffed cereal or puffed rice, should be crushed. You may need to crush multiple pieces of this type of food to ensure the sample meets the recommended pea-sized. This this type of food is full of air, crushing only a small amount may not yield a large enough sample in this specific case.